The problems caused by internal gas leakage in the engine have been explained in the U.S. Pat. No. 3,927,529, which also contains one solution of the problem, viz. a connection between a space confined between two piston rings of a piston and its hollow dome. This solution of the problem is an effective and practical scheme for most applications. However, in automotive applications, where it is common practice to govern the power output of a Stirling cycle engine by adjusting the mean pressure of the working gas charges, the engine volumes containing working gas should be kept as small as possible so that the power output may be changed rapidly.
Changes in mean gas pressure require the use of a compressor, and in the interests of efficiency and fast response time, the work to be exerted by the compressor should be as small as possible. Although the gas contained in the hollow piston domes does not form an active part of the working gas charges and does not participate in the pressure fluctuations of the Stirling cycle, it does contribute to the total gas content, which has a negative effect on the power control responsiveness and on the compressor work.